What is a Virus ?

The full name of AIDS virus is Acquired Immuno Deficiency Syndrome. This disease is caused by a virus. Viruses that spreads AIDS are known by following different names:
- Human T lymphotropic Virus III (HLV-III)
- Lymphadenopathy associated virus (LAV)
- AIDS related retrovirus (ARV)

Numerous bacteriophages are present in the water of river Ganga. They destroy the pathogenic bacteria present in the polluted water of the river. Therefore, they keep the water of the river Ganga pure by working as a scavenger. And these viruses that infect and kill bacteria could provide a useful alternative to antibiotics in the form of phage therapy.

Viruses are not alive: They do not have cells, they cannot turn food into energy, and without a host they are just inert packets of chemicals.

We are family: Scientists suspect that a large DNA-based virus took up residence inside a bacterial cell more than a billion years ago to create the first cell nucleus. If so, then we are all descended from viruses.

Although, viruses are the causative agent of several diseases. But on the other hand they are also use as bacteriophage to destroy harmful bacteria from the water. Therefore, Phage therapy is the use of bacteriophages to treat pathological (disease-causing) infections caused by bacteria.

Certain types of cancers have been linked to cancer viruses. Burkitt's lymphoma, cervical cancer, liver cancer, T-cell leukemia, and Kaposi sarcoma are examples of cancers that have been associated with different types of viral infections. The majority of viral infections, however, do not cause cancer.

Viruses are not exactly dead, either: They have genes, they reproduce, and they evolve through natural selection

All viruses have a protein coating or capsid, but some viruses, such as the flu virus, have an additional membrane called an envelope. Viruses without this extra membrane are called naked viruses. The presence or absence of an envelope is an important determining factor in how a virus interacts with the host's membrane, how it enters a host, and how it exits the host after maturation

Scientists have been debating this issue since 1892, when Dmitry Ivanovsky, a Russian microbiologist, reported that an infection in tobacco plants spreads via something smaller than a bacterium.

That something, now called the tobacco mosaic virus, appears on this page (magnified and colorized).

Enveloped viruses can enter the host by fusion with the host membrane to release their genetic material into the cytoplasm, while naked viruses must enter a cell through endocytosis by the host cell. Enveloped viruses exit by budding or exocytosis by the host, but naked viruses must lyse (break open) the host cell to escape.

Score one for Team Nonliving: After American biochemist Wendell Stanley purified the tobacco mosaic virus into needlelike crystals of protein, he won a 1946 Nobel Prize—awarded in chemistry, not medicine

1 Viruses are not alive: They do not have cells, they cannot turn food into energy, and without a host they are just inert packets of chemicals.

There Are 2 Classes of Viruses
Viruses can contain single-stranded or double-stranded DNA as the basis for their genetic material, and some even contain single-stranded or double-stranded RNA. Furthermore, some viruses have their genetic information organized as straight strands, while others have circular molecules. The type of genetic material contained in a virus not only determines which types of cells are viable hosts but also how the virus is replicated.

2  Viruses are not exactly dead, either: They have genes, they reproduce, and they evolve through natural selection.

3  Scientists have been debating this issue since 1892, when Dmitry Ivanovsky, a Russian microbiologist, reported that an infection in tobacco plants spreads via something smaller than a bacterium.

A Virus Can Remain Dormant in a Host for Years
Viruses undergo a life cycle with several phases. The virus first attaches to the host via specific proteins on the cell surface. These proteins are generally receptors that differ depending on the type of virus targeting the cell. Once attached, the virus then enters the cell by endocytosis or fusion.

Some viruses sneak DNA into a bacterium through its, um, sex appendage, a long tube known as a pilus.

That something, now called the tobacco mosaic virus, appears on this page (magnified and colorized).

Virus comes from the Latin word for “poison” or “slimy liquid,” an apt descriptor for the bug that causes flu and the common cold.

The host's mechanisms are used to replicate the DNA or RNA of the virus as well as essential proteins. After these new viruses mature, the host is lysed to allow the new viruses to repeat the cycle.

An additional phase before replication, known as the lysogenic or dormant phase, occurs in only a select number of viruses.

4  Score one for Team Nonliving: After American biochemist Wendell Stanley purified the tobacco mosaic virus into needlelike crystals of protein, he won a 1946 Nobel Prize—awarded in chemistry, not medicine.

In 1992 scientists tracking a pneumonia outbreak in England found a massive new kind of virus lurking within an amoeba inside a cooling tower.

5  Score one for Team Living: Some viruses sneak DNA into a bacterium through its, um, sex appendage, a long tube known as a pilus. If that’s not life, what is?

During this phase, the virus can remain inside the host for extended periods of time without causing any apparent changes in the host cell. Once activated, however, these viruses can immediately enter the lytic phase in which replication, maturation, and release can occur. HIV, for example, can remain dormant for 10 years.